Mr. Sanders, who’s running to Hillary Clinton’s left for the Democratic presidential nomination, told MSNBC’s Rachel Maddow that he wasn’t surprised by Planned Parenthood’s decision to endorse the former secretary of state.

“So I have friends and supporters in the Human Rights [Campaign] Fund and Planned Parenthood. But you know what? Hillary Clinton has been around for a very, very long time,” he said during a Tuesday night appearance. “Some of these groups are, in fact, part of the establishment.”

Former President Bill Clinton seized on the comment in a Wednesday campaign appearance in New Hampshire, where Mr. Sanders is leading by 27 points in the most recent WMUR/CNN poll.

“Hillary Clinton does not consider Planned Parenthood a member of the establishment,” Mr. Clinton said as reported by ABC News.

The leftist feminist group UltraViolet rebuked Mr. Sanders in a Wednesday statement, saying Planned Parenthood is “not a political football to be tossed around for political gain — by Democrats or Republicans.”

“At this time when Planned Parenthood, and women’s health care in general, is under daily attack from Republicans and right wing extremists, the choice by Sen. Sanders to malign such an important organization for women on national television is particularly disappointing,” said the statement by UltraViolet co-founder Nita Chaudhary.

“Really Senator Sanders? How can you say that groups like @ppAct and @HRC are part of the ‘establishment’ you’re taking on? -H” said the Tweet on @HillaryClinton.

Mr. Sanders made his comment in response to a question from Ms. Maddow, who asked whether he had sought the endorsement of groups like Planned Parenthood and the Human Rights Campaign, which have endorsed Ms. Clinton.

“Rachel, I would love to have the endorsement of every progressive organization in America,” he said but that “we’re taking on not only Wall Street and the economic establishment, we’re taking on the political establishment.”